Objective: The aim of this study was to compare clinically between full mouth debridement and partial mouth debridement with or without adjunctive use of systemic azithromycin in patients with mild-moderate chronic periodonitis.Subjects and methods: This study was conducted on 60 individuals who were suffering from mild to moderate chronic periodontitis which were equally divided into4 groups: group (A) of patients were treated by partial mouth scaling and root planing with azithromycin, 500mg once a day for three days before periodontal treatment. Group (B) included patients treated with partial mouth scaling and root planning of the whole mouth alone. As for group (C),patients received full mouth scaling and root planning and azithromycin. Finally, Group (D) included patients treated with full mouth scaling and root planing alone.Results: Comparing the percentage reduction in PPD and CAL gain in the treated sites, there was no statistically significant difference between the 4 groups at 1 month, at 3 months and at 6 months. In addition, at baseline, after 1 month, 3 months and 6 months, there was no statistically significant difference between means mm PPDs of the 4 studied groups. The results of this investigation showed that there was a statistically significant difference in mean mm PPD reduction after1 month, 3 months and after 6 months in all groups compared to baseline values. Same results were also shown regarding the mean CAL. Conclusion: Scaling and root planing (partial and full mouth) with and without the adjunctive use of azithromycin proved to be effective and efficient in treating mild to moderate chronic periodontitis.The adjunctive use of AZM provided no additional benefit over SRP alone. Full mouth scaling and root planing was found to be as effective as partial mouth scaling and root planing regarding PPD reduction and CAL gain.